Various types of optical devices are incorporated into a wide range of consumer and industrial products and systems. One such device is an optical proximity sensor, which can be integrated, for example, into a mobile, hand-held cell phone. The proximity sensor can be used to sense whether the cell phone is held close to the user's ear (e.g., during a phone call) and to cause the phone's display to switch off so as to reduce power consumption or to prevent unintended activation of icons on the screen. If the phone is moved away from the user's ear, the proximity sensor can detect that situation and cause the display to switch on and allow icons to be activated.
Testing of such optical devices is important to ensure that they function properly and satisfy any required specifications. In general, it can be advantageous to test the optical devices after they are integrated into the end-products so as to allow the devices to be tested in the environment in which they will be used. On the other hand, doing so can increase overall cost and result in the need to remove devices that do not meet the tests in a satisfactory way.